1. Field of the Invention
The present invention relates to a multi color image forming apparatus such as a color laser printer and an image making device used therein.
2. Background Art
As a color laser printer based on the electrophotography, a so-called tandem color laser printer is well known in which the photosensitive drums are provided corresponding to the toners of yellow, magenta, cyan and black color. In such tandem color laser printer, a toner image for each color is formed on each photosensitive drum at the almost same time, so that the color image is formed at the almost same speed as the monochrome printer.
However, in the tandem color laser printer, the arrangement of fixing units for fixing a color toner image transferred onto the paper is needed to examine to reduce the size of apparatus.
That is, for example, in a direct transfer method in which a toner image for each color formed on each photosensitive drum is directly transferred onto the paper, the fixing units are usually provided sideways on the downstream side of a paper conveying belt that is opposed to the photosensitive drums disposed in parallel. However, there is the drawback that the image forming apparatus is very long in its parallel direction, because in addition to the length of the photosensitive drums disposed in parallel, the fixing units are provided in the parallel direction.
On the other hand, in an intermediate transfer method in which a toner image for each color formed on each photosensitive drum is once transferred onto an intermediate transfer belt to form a color toner image, and the color toner image formed on the intermediate transfer belt is transferred onto the paper by a secondary transfer roller, the photosensitive drums are disposed in parallel above the intermediate transfer belt in the almost horizontal direction, and the fixing units are disposed beneath the intermediate transfer belt, thereby preventing the image forming apparatus from being longer in the parallel direction of the photosensitive drums, as described in JP-A-2001-272833.
By the way, when the photosensitive member is charged by discharge of a charging wire in the charger of the multicolor image forming apparatus, a discharge product (mainly ozone) is produced. When this ozone adheres to the surface of the photosensitive member, an unevenness of charge occurs on the photosensitive member, and has some adverse influence such as an image drift on the image formed in the multicolor image forming apparatus.
Therefore, the multicolor image forming apparatus of this type may be provided with a duct for exhausting ozone to exhaust ozone from the side face of the multicolor image forming apparatus to the outside (e.g., refer to JP-A-2002-196635).